1. Field of the Invention
This invention relates to a geographic information indicator using a system composed of a database server computer and a client computer installed on Internet or Intranet, and more particularly to a geographic information indicator for displaying geographic information stored in the database server computer on the client computer. This invention further relates to a method for displaying geographic information stored in the database server computer on the client computer and a storage medium for storing a program for executing it.
2. Description of the Related Art
FIG. 18 is a block diagram of a conventional geographic information indicator using a system composed of a database server 2, a WWW (world-wide web) 3 and a client computer 1 installed on Internet or Intranet. The database server 2 executes the retrieval process for a database inquiry received from the client computer 1 via the WWW server 3 on a master database 21 in the database server 2 and returns the result thereof to the client computer 1 via the WWW server 3.
The WWW server 3 relays data between the client computer 1 and the database server 2. The client computer 1 is composed of a screen display request input means 11, a server-side database retrieval request means 14, a screen display means 18, a data cache management means 121, and a data cache 120.
A WWW browser is used for the client computer 1. In the data cache 120, a set of an inquiry sent from the client computer 1 to the database server 2 in the past via the WWW server 3 and the retrieval result thereof returned to the client computer 1 from the database server 2 via the WWW server 3 is stored. The screen display request input means 11 inputs a screen display request from a user.
The data cache management means 121 checks by retrieving the data cache 120 whether or not the same inquiry as the screen display request received from the screen display request input means 11 was made in the past. When the same inquiry was made in the past, the data cache management means 121 obtains the retrieval result from the data cache 120 and transfers it to the screen display means 18.
When such an inquiry was not made in the past, an inquiry is made to the database server 2 from the server-side database retrieval request means 14 via the WWW server 3. When the retrieval result by the database server 2 is returned to the client computer 1 via the WWW server 3, the data cache management means 121 newly adds a set of the inquiry and retrieval result to the data cache 120. The retrieval result by the database server 2 is displayed by the screen display means 18.
In the aforementioned prior art, when the information requested by the screen display request in this time is the same as the information requested once in the past, the requested information can be displayed using the data stored in the data cache without inquiring the database server once again. However, when the display request range is deviated from the range requested once in the past, even if an inquiry is made for the data in the greater part of the area of the display request range in the past, another inquiry is required to be made for the overall area of the display request range to the database server. As a result, it takes a lot of time for the data transfer.
Furthermore, when a screen display request is made for the display range overlapping with the past display range, a number of data overlapping with data obtained in the past must be stored in the data cache. As a result, the utilization factor of the data cache is reduced.
Accordingly, one object of this invention is to provide a geographic information indicator, a method for displaying geographic information and a storage medium for storing program for executing the same which can shorten the data transfer time without inquiring the database server once again about the information displayed once.
Another object of this invention is to provide a geographic information indicator, a method for displaying geographic information and a storage medium for storing program for executing the same which can increase the utilization factor of the database.
These and other objects of this invention can be achieved by providing a geographic information indicator for displaying an information obtained from a database server for storing the information of a map and facilities to be arranged on the map via a network, including a local database for storing a data obtained from the database server by an inquiry, and screen display request input means for inputting a screen display request by designating a screen display range. The geographic information indicator further includes means for storing a range within which the data is stored in the local database in a form of a local database effective range information, the range being represented by overlapping a plurality of areas, local database effective range check means for deciding a first area within which the data is already stored in the local database and a second area within which the data is not stored in the local database out of the designated screen display range based on the local database effective range information, and server-side database retrieval request means for inquiring the database server via the network about the data included in the second area based on a decision result of the local database effective range check means. The geographic information indicator also includes local database update means for additionally storing the data obtained as a retrieval result from the database server via the network in the local database and also updating the local database effective range information based on the second area, local database retrieval means for extracting the data included in the screen display range necessary for screen display from the data stored in the local database, and screen display means for displaying the data extracted from the local database on a screen.
According to one aspect of this invention, there is provided a geographic information indicator for displaying an information obtained from a database server for storing the information of a map and facilities to be arranged on the map via a network including a local database for storing a data obtained from the database server by an inquiry, and screen display request input means for inputting a screen display request in a form of a rectangular range. The geographic information indicator further includes means for storing an effective range within which the data is stored in the local database in a form of a local database effective range information, the effective range being represented by overlapping a plurality of the rectangular ranges, local database effective range check means for deciding a first range expressed in the form of the rectangular range within which the data is already stored in the local database and a second range expressed in the form of the rectangular range within which the data is not stored in the local database out of the rectangular range designated by the screen display request based on the effective range in the local database effective range information, and server-side database retrieval request means for inquiring the database server via the network about the data included in the second range based on a decision result of the local database effective range check means. The geographic information indicator also includes local database update means for additionally storing the data obtained as a retrieval result from the database server via the network in the local database, and also for updating the effective range in the local database effective range information based on the rectangular range, local database retrieval means for extracting the data included in the rectangular range from the data stored in the local database, and screen display means for displaying the data extracted from the local database on a screen.
According to another aspect of this invention, there is provided a program storing medium readable by a computer, tangibly embodying a program of instructions executable by the computer to perform method steps for a geographic information indicator for displaying a data stored in a local database which is obtained from a database server for storing an information of a map and facilities to be arranged on the map via a network. The method includes the steps of a screen display request input step for inputting a screen display request by designating a screen display range, and a step for storing a range within which the data is stored in the local database in a form of a local database effective range information, the range being represented by overlapping a plurality of areas. The methods further includes a local database effective range check step for deciding a first area within which the data is already stored in the local database and a second area within which the data is not stored in the local database out of the designated screen display range based on the local database effective range information, and a server-side database retrieval request step for inquiring the database server via the network-about the data included in the second area based on a decision result of the local database effective range check step. The method further includes a local database update step for additionally storing the data obtained as a retrieval result from the database server via the network in the local database and also updating the local database effective range information based on the second area, a local database retrieval step for extracting the data included in the screen display range necessary for screen display from the data stored in the local database, and a screen display step for displaying the data extracted from the local database on a screen.
According to still another aspect of this invention, there is provided a method for indicating a geographic information to supply a user a data stored in a local database which is obtained from a database server for storing an information of a map and facilities to be arranged on the map via a network. The method includes the steps of a step for urging the user to input a screen display request along with a screen display range, and a step for storing a range within which the data is stored in the local database in a form of a local database effective range information, the range being represented by overlapping a plurality of areas. The method further includes a step for deciding a first area within which the data is already stored in the local database and a second area within which the data is not stored in the local database out of the designated screen display range based on the local database effective range information, a step for inquiring the database server via the network about the data included in the second area based on a decision result. The method also includes a step for additionally storing the data obtained as a retrieval result from the database server via the network in the local database and also updating the local database effective range information based on the second area, a step for extracting the data included in the screen display range necessary for screen display from the data stored in the local database, and a step for transmitting the data extracted from the local database to a terminal of the user.